This exploratory biobehavioral pain research will study differences anxiety pain in dental and in natural red-haired men and women compared with dark-haired men and women. Red hair results from mutations of the melanoncortin-1 receptor gene (MC1R). Our specific aims are to 1) determine the association between perceived dental pain, dental anxiety, and dental utilization with MC1R gene status and hair color; 2) determine experimental pain thresholds and dose-dependent local anesthetic sensitivity as a function of hair color and MC1R gene variation in volunteers; and 3) determine local anesthetic requirement for restorative dental treatment as a function of hair color and MC1R gene variation. This proposal is collaboration between the School of Dentistry, the Department of Anesthesiology, the OUTCOMES RESEARCH Institute, the Genetics Core Laboratory, and the Department of Psychology -- all at the University of Louisville. All participating male and female subjects will be genotyped for MC1R alleles, and new technology will be used that provides consistent and objective assessment of dental pain. The study will be accomplished in three phases: 1) In the Observational Phase, 74 redheads and 74 dark-haired participants (aged 18 to 40) will each complete validated survey instruments designed to measure psychological symptomatology, global and dental-specific anxiety, constructs associated with dental pain and avoidance (e.g., anxiety and pain sensitivity), and previous dental history including dental care utilization. 2) In the Experimental Phase, we will recruit 60 redheaded and 60 dark-haired volunteers from those completing the Observational phase. Pain, perceived as a result of electrical current and thermal stimuli on unrestored lateral incisor teeth, will be measured after intra-oral injection of various lidocaine concentrations. The concentrations, which will be used in a randomized and double-blinded sequence, will be 0, 0.5, 1.0, and 1.5%. And 3) in the Clinical Phase, we will recruit 60 redheaded and 60 dark-haired volunteers requiring non-surgical dental treatment from those completing the Observational phase. We will use the Dixon "up-and-down" method to determine local anesthetic requirement in each group. The proposed research will contribute to the knowledge of the role of gender and genetics in peripheral nerve function, pain perception, and behavior. The research will also explore the feasibility of an innovative dental pain assessment approach that may provide a basis for future research projects and could guide the development of biobehavioral interventions to manage dental anxiety and prevent pain.